2D water effect with GLSL and SFML

gistfile1.cpp

const char sinShader[] =
	"#version 120\n"
	"uniform float time = 1.0;"

	"void main(void)"
	"{"
		"const float sinWidth = 0.08;"
		"const float sinHeight = 0.04;"
		"const float timeMulti = 10.0;"
		"const float val = (sin(gl_FragCoord.x * sinWidth + time * timeMulti) + sin(gl_FragCoord.y * sinHeight + time * timeMulti)) * 0.3 + 0.5;"

		"gl_FragColor = vec4(vec3(val), 1.0);"
	"}";

const char dudvShader[]=
	"#version 130\n"
	"uniform sampler2D texture;"
	"uniform sampler2D heightmap;"
	"const vec2 size = vec2(2.0, 0.0);"
	"const ivec3 offset = ivec3(-1, 0, 1);"
	"void main(void)"
	"{"
		"vec2 coord = gl_TexCoord[0].xy;"
		"float s01 = textureOffset(heightmap, coord, offset.xy).x;"
		"float s21 = textureOffset(heightmap, coord, offset.zy).x;"
		"float s10 = textureOffset(heightmap, coord, offset.yx).x;"
		"float s12 = textureOffset(heightmap, coord, offset.yz).x;"
		"vec3 va = normalize(vec3(size.xy, s21 - s01));"
		"vec3 vb = normalize(vec3(size.yx, s12 - s10));"
		"vec2 dudv = cross(va, vb).rg;"

		"gl_FragColor = texture2D(texture, coord + dudv * 0.2);"
	"}";

#include <SFML/System.hpp>
#include <SFML/Window.hpp>
#include <SFML/Graphics.hpp>


int main()
{
	sf::RenderWindow renderWindow(sf::VideoMode(800u, 600u), "");
	renderWindow.setVerticalSyncEnabled(true);

	sf::Clock frameClock, shaderClock;

	
	sf::Shader sinEffect;
	sinEffect.loadFromMemory(sinShader, sf::Shader::Fragment);
	sf::RectangleShape rect(sf::Vector2f(600.f, 600.f));
	sf::RenderTexture rt;
	rt.create(600, 600);

	sf::Shader dudvEffect;
	dudvEffect.loadFromMemory(dudvShader, sf::Shader::Fragment);
	dudvEffect.setParameter("heightmap", rt.getTexture());
	sf::Texture texture;
	texture.loadFromFile("assets/textures/crate.jpg");
	texture.setRepeated(true);
	sf::Sprite sprite(texture);

	//-----------------------------------//

	while(renderWindow.isOpen())
	{
		//poll input
		sf::Event event;
		while(renderWindow.pollEvent(event))
		{
			if (event.type == sf::Event::Closed)
				renderWindow.close();
			if(event.type == sf::Event::KeyReleased)
			{
				switch(event.key.code)
				{
				case sf::Keyboard::D:

					break;
				default: break;
				}
			}
        }

		//update shader
		sinEffect.setParameter("time", shaderClock.getElapsedTime().asSeconds());

		//draw
		frameClock.restart();

		rt.clear();
		rt.draw(rect, &sinEffect);
		rt.display();

		renderWindow.clear();
		//renderWindow.draw(sf::Sprite(rt.getTexture())); //draws height map
		renderWindow.draw(sprite, &dudvEffect);
		renderWindow.display();

		renderWindow.setTitle(std::to_string(1.f / frameClock.getElapsedTime().asSeconds()));
	}

	return 0;
}